Enhanced frequency diversity technique for systems with carrier aggregation

ABSTRACT

A technique is provided to interleave data and control signals across a plurality of component carriers to achieve frequency diversity in conjunction with carrier aggregation.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/318,696, filed Mar. 29, 2010.

TECHNICAL FIELD OF THE INVENTION

This application relates to wireless communication, and more toparticularly to the implementation of carrier aggregation in wirelesscommunication.

BACKGROUND

The famous Shannon's law for communication establishes a linearproportionality between available channel bandwidth and the amount ofdata that can be transmitted through the corresponding channel. Asdetermined by this law, higher data rates require more bandwidth at agiven signal-to-noise ratio (SNR) as opposed to lower data ratecommunications at the same SNR. But a given amount of bandwidth has arelative amount of worth: signal attenuation is markedly higher asfrequency increases. Thus, it is better to have bandwidth in theregulated spectrums such as at 700 MHz as opposed to having the sameamount of bandwidth in the unregulated higher frequency bands such as at2.4 GHz.

Despite the scarceness of desirable spectrums for wirelesscommunications, the requirement for additional bandwidth is everincreasing. Indeed, regardless of the particular frequency for wirelesscommunication, the need for bandwidth is non-negotiable if one wants toachieve higher data rates. Modern 4G telecommunication protocols such asLong Term Evolution-Advanced (LTE-A) are proposing 1 Gps (one billionbits per second) downlink data rates or even higher. But it is difficultto achieve such a data rate in the limited communication bandwidths thatare available to a wireless carrier, particularly in the desirable“beachfront” spectrums such as 700 MHz. For example, the currentgeneration of LTE uses orthogonal subcarriers spread across a channelbandwidth that may range from 1.4 MHz to a maximum of 20 MHz. Thesubcarriers are separated by 15 KHz such that the maximum symbol ratefor each subcarrier is thus 15,000 symbols/second. The number of bitsper symbol depends upon the modulation scheme—LTE supports a maximum of64 bits per symbol using 64QAM. Thus, the 20 MHz channel of LTE supportsa raw data rate of 108 Mbps. The actual data rate will depend uponcoding overhead and other variables. One can thus appreciate that ifLTE-A is to achieve a 1 Gps data rate, the channel bandwidth must beincreased by multiples of the LTE 20 MHz channel But note that backwardcompatibility with conventional LTE should be maintained. Thus, carrieraggregation in LTE-A involves the use of multiple 20 MHz channels. To aconventional LTE handset (which may be designated as user equipment(UE)), each 20 MHz channel operates as a conventional LTE channel. Butto an LTE-A UE, data can be received across multiple combinations ofsuch channels. Since each LTE channel corresponds to an LTE carrier, theLTE carrier becomes a component carrier for an LTE-A UE. Carrieraggregation thus preserves precious bandwidth resources for conventionallower-data-rate communication yet achieves greater bandwidth resourcesfor high-data-rate communication.

One of the main technical challenges for implementing carrieraggregation in LTE-Advanced systems is the backward compatibilityrequirement with the current LTE systems. The additional bandwidthprovided by carrier aggregation provides an opportunity for frequencydiversity. But because of the complications raised by the need forbackwards compatibility, existing carrier aggregation schemes do notexploit frequency diversity. Instead, conventional carrier aggregationsschemes enjoy frequency diversity only within each component carrier—forexample, a conventional uplink LTE channel is interleaved. Accordingly,there is a need in the art for improved carrier aggregation schemes thatexploit the opportunity for frequency diversity across the componentcarriers rather than just within each component carrier.

SUMMARY

In accordance with an aspect of the disclosure, a method is providedthat includes the acts of providing a plurality of transport blocks,each transport block corresponding to a component carrier (CC); in abaseband processor, channel coding each transport block into acorresponding channel-coded data signal; in the baseband processor,bit-combining the channel-coded data signals into a bit-combined datasignal; and in the baseband processor, interleaving the bit-combineddata signal to produce an interleaved plurality of code words.

In accordance with another aspect of the disclosure, a downlink methodis provided that includes the acts of determining whether a plurality ofcomponent carriers are being interleaved; if a plurality of componentcarriers are being interleaved, bit-combining a plurality ofchannel-coded data signals to form a bit-combined data signal; writingthe bit-combined data signal into an interleaver matrix stored within amemory, wherein the interleaver matrix is arranged into a plurality ofsub-matrices corresponding to the plurality of component carriers;reading from each sub-matrix to retrieve a corresponding output datasignal; and modulating each component carrier according to thecorresponding output data signal.

In accordance with yet another aspect of the disclosure, a wirelessdevice, is provided that includes a memory; a baseband processorconfigured to channel code a plurality of transport blocks into acorresponding plurality of channel-coded data signals, bit-combine thechannel-coded data signals into a bit-combined data signal, write thebit-combined data signal into an interleaver matrix stored within thememory, and to read from the interleaver matrix to produce aninterleaved data signal; and a radio-frequency integrated circuit (RFIC)configured to modulate an RF carrier signal according to the interleaveddata signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the transport block processing modules for an LTEuplink shared channel.

FIG. 2 is a flowchart for the interleaver operation performed withregard to FIG. 1.

FIG. 3 illustrates the transport block processing modules for an LTEdownlink shared channel.

FIG. 4 illustrates the transport block processing modules and channelinterleaver for uplink shared channel with carrier aggregation.

FIG. 5 is a flowchart for the interleaver operation performed withregard to FIG. 4.

FIG. 6 illustrates the transport block processing modules and channelinterleaver for a downlink shared channel with carrier aggregation.

FIG. 7 is a flowchart for the interleaver operation performed withregard to FIG. 6.

FIG. 8 is a block diagram of a wireless device configured to achievefrequency diversity through carrier aggregation in accordance witheither the downlink or uplink embodiments of FIGS. 1-7.

DETAILED DESCRIPTION

Frequency diversity carrier aggregation is described herein with regardto a Long Term Evolution Advanced (LTE-A) implementation. However, itwill be appreciated that the principles of the disclosed carrieraggregation are readily applicable to other wireless communicationprotocols such as WiMax. The carrier aggregation of the presentapplication is denoted as frequency diversity carrier aggregation inthat frequency diversity across the aggregated component carriers isadvantageously achieved yet backwards compatibility with conventionalLTE (no carrier aggregation) is maintained. This compatibility is bestunderstood with regard to the shared channel, which is used to transmitboth data and some control information.

The shared channel data and control information passes from the MAClayer in LTE systems to the physical (PHY) layer through transportchannels, which form the interface between the MAC and PHY layers. Theuplink and downlink transport channels process data in transport blocks,which are groups of resource blocks sharing a common modulation andcoding implementation. In addition to a shared transport channel in boththe uplink and downlink, there are other types of transport channelssuch as a broadcast channel and a random access channel. But since thefocus of carrier aggregation is to increase data rate, only thedata-carrying shared channels are discussed herein. To illustrate thedifficulties of maintaining backward compatibility, the LTE conventionalprocessing of the downlink and uplink shared channels will be discussedand contrasted with the carrier aggregation processing for thesechannels. The uplink shared transport channel will be discussed firstfollowed by the downlink shared transport channel

Uplink Transport Channel Processing in LTE

Turning now to the drawings, the transport channel processing for aconventional LTE uplink shared channel (UL-SCH) is illustrated inFIG. 1. This transport channel processing occurs as set forth in 3GPP TS36.212 Multiplexing and Channel Coding (Release 9), which willhereinafter be referred to simply as “LTE Release 9” and is incorporatedherein in its entirety. Data arrives at a CRC attachment coding unit 100in the as a maximum of one MAC protocol data unit (PDU) everytransmission time interval (TTI). The data portion of a MAC PDU may berepresented by a vector a₀, a₁, a₂ a₃, . . . a_(A-1) that is A bitslong. Coding unit 100 calculates a corresponding number L of parity bitsp₀, p₁, p₂, p₃, . . . , p_(L-1), where L is determined by the particularCRC length. In LTE, L can be either sixteen or twenty-four bits. Thebits produced by CRC attachment coding unit 100 are represented by avector b₀, b₁, b₂, b₃, . . . , b_(B-1) of length B, where B equals Aplus L. The length B for this vector may be too long for a subsequentchannel coding step that may accommodate only Z bits. This if Z is lessthan B, the output from coding unit 100 is processed into shorter blockswith an additional CRC attachment in code block segmentation and CRCattachment module 105. The output from module 105 may be represented bya vector c_(r) ₀ , c_(r) ₁ , c_(r) ₂ , c_(r) ₃ , . . . , c_(r(E) _(r)⁻¹⁾ of length K_(r). A channel coding module 110 receives the outputfrom module 105 and applies the appropriate turbo coding to producemultiple output signals ranging from an i=0 to an i=1 channel-codedsignal, where the 1^(th) channel-coded signal may be represented by avector d_(r) ₀ ^((i)), d_(r) ₁ ^((i)), d_(r) ₂ ^((i))d_(r) ₃ ^((i)), . .. , d_(r(D) _(r) ⁻¹⁾ ^((i)) of length D_(r)=K_(r)+1. A rate matchingmodule 115 interleaves the channel-coded signals from the channel coderand performs bit selection and pruning to produce an output signalrepresented by a vector e_(r) ₀ , e_(r) ₁ , e_(r) ₂ , e_(r) ₃ , . . . ,e_(r(E) _(r) ⁻¹⁾ of length E_(r) for code block r. A code blockconcentration module 121 concatenates the rate matching outputs for thedifferent code blocks to produce an output signal represented by avector f₀, f₁, f₂, f₃, . . . , f_(G-1) of length G.

The control data for the transport block arrives at channel codingmodule 110 in three forms: channel quality information (CQI), rankindication (RI), and hybrid automatic repeat request acknowledgment(HARQ-ACK). The corresponding channel coded signals are represented byvectors q₀ ^(ACK), q₁ ^(ACK), . . . , q_(Q′) _(ACK) ⁻¹ ^(ACK) for thecoded HARQ-ACK data [q′₀ ^(RI), q′₁ ^(RI)q′₂ ^(RI), . . . , q′_(NG′)^(RI) ⁻¹ ^(RI)] for the coded RI data, and q₀ ^(RI), q₁ ^(RI), q₂ ^(RI),. . . , q_(Q′) _(RI) ⁻ ^(RI) for the coded CQI/PMI data. For frequencydiversity exploitation of carrier aggregation, interleaved codedmodulation may be used to capture the frequency diversity. Consequently,channel coding module 110 and rate matching module 115 (which includesan internal sub-block interleaver for the received data signals) aremost relevant to frequency diversity exploitation. Since there is alsocontrol information as discussed above that is transmitted in the uplinkshared channel, a channel interleaver 120 across the data and controlinformation is applied in the uplink shared channel. This is a simplesymbol interleaver where modulation symbols are written to a rectangularmatrix row-by-row and read out column-by-column.

Prior to interleaving, the CQI encoded sequence (represented by thevector q₀ ^(RI), q₁ ^(RI), q₂ ^(RI), . . . q_(Q′) _(RI) ⁻¹ ^(RI)) ismultiplexed with the uplink shared data (represented by vector e_(r) ₀ ,e_(r) ₁ , e_(r) ₂ , . . . , e_(r(E) _(r) ⁻¹⁾) in a data and controlmultiplexer 125 to produce a multiplexed output signal represented byg₀, g₁, g₂, . . . , g_(H′−1), where H′=H/Q_(m) and H=(G+Q_(cQt)), andwhere g_(i), i=0, . . . , H′−1 are column vectors of length Q_(m)corresponding to the modulation order. In this fashion, data and controlinformation are mapped to different modulation symbols. H is the totalnumber of coded bits allocated for UL-SCH data and CQI/PMI information.As further discussed in LTE Release 9, the control information and thedata shall be multiplexed in multiplexer 125 according to the followingpseudocode:

Set i,j, k to 0 while j < Q_(CQI) -- first place the control information    g _(k) = [q_(j) ...q_(j+Qm) ⁻¹]^(T)     j = j + Q_(m)     k = k + 1end while while i < G -- then place the data     g _(k) = [f_(i) ...f_(i+Qm) ⁻¹]^(T)     i = i + Q_(m)     k = k + 1 end while

Channel interleaver 120 interleaves such that HARQ-ACK indications arepresent on both slots in a subframe. The number of modulation symbols ineach subframe is given by H″=H′+Q′_(RI). As defined by LTE Release 9, anoutput bit sequence from interleaver 120 represented by h₀, h₁, h₂, . .. , h_(H+Q) _(RI) ⁻¹. To produce this interleaved output, interleaver120 may be considered to construct a matrix of output signals that arewritten row-by-row into a memory or buffer but read out from memorycolumn-by-column. The number of columns for this output matrix frominterleaver 120 is C_(mux)=N_(symb) ^(PUSCH). The column s of the matrixare numbered 0,1,2,K,C_(mux)−1 from left to right, and N_(symb) ^(PUSCH)is determined as discussed in section 5.2.2.6 of LTE Release 9. Thenumber of rows of the interleaver output matrix isR_(mux)=(H″·Q_(m))/C_(mux), and LTE Release 9 definesR′_(mux)=R_(mux)/Q_(m). The rows of the interleaver output matrix arethus numbered 0,1,2, K, R_(mux)−1 from top to bottom. The interleavingprocess performed by interleaver 120 is illustrated in FIG. 2. Aninitial step 200 determines what type of information is being currentlyinterleaved—in other words, whether the information being interleaved isthe multiplexed data and CQI, rank indication (RI), or HARQ-ACKinformation. If RI information is transmitted in the current subframe,interleaver 120 will first process the RI information prior toprocessing the multiplexed data and CQI. Thus, if step 200 indicatesthat data and CQI is currently being processed, a step 205 determineswhether the RI information (if present) has been already interleavedinto the output matrix. If step 200 indicates that RI information isbeing processed, the RI information is written into the output matrix ina step 210 as follows. The vector sequence q₀ ^(RI), q₁ ^(RI), q₂ ^(RI),. . . , q_(Q′) _(RI) ⁻¹ ^(RI) is written into the columns as indicatedby Table I below, and by sets of Q_(m) rows starting from the last rowand moving upwards according to the following pseudo code:

Set i,j to 0. Set r to R′_(mux) −1 while i < Q′_(RI) c_(RI) = ColumnSet(j) y _(r×C) _(mux) ₊ _(c) _(R1) = q _(i) ^(RI) i = i + 1 r =R′_(mux) −1−└i/4┘ j = (j + 3)mod 4 end whileThe variable Column Set is given in Table 1 and indexed left to rightfrom 0 to 3.

Having thus written the RI data to the output matrix (if there is suchdata to be written), interleaver 120 may then process the multiplexeddata and CQI information in a step 215 as follows: interleaver 120writes the input vector sequence, for k=0, 1, . . . H′−1, into the(R_(mux)×C_(mux)) matrix by sets of Q_(m) rows starting with the vectory₀ in column 0 and row 0 to (Q_(mux)−1) and skipping the matrix entriesthat are already occupied:

$\begin{bmatrix}{\underset{\_}{y}}_{0} & {\underset{\_}{y}}_{1} & {\underset{\_}{y}}_{2} & \ldots & {\underset{\_}{y}}_{C_{mux} - 1} \\{\underset{\_}{y}}_{C_{mux}} & {\underset{\_}{y}}_{C_{mux} + 1} & {\underset{\_}{y}}_{C_{mux} + 2} & \ldots & {\underset{\_}{y}}_{{2C_{mux}} - 1} \\\vdots & \vdots & \vdots & \ddots & \vdots \\{\underset{\_}{y}}_{{({R_{mux}^{\prime} - 1})} \times C_{mux}} & {\underset{\_}{y}}_{{{({R_{mux}^{\prime} - 1})} \times C_{mux}} + 1} & {\underset{\_}{y}}_{{{({R_{mux}^{\prime} - 1})} \times C_{mux}} + 2} & \ldots & {\underset{\_}{y}}_{({{R_{mux}^{\prime} \times C_{mux}} - 1})}\end{bmatrix}\quad$

The pseudocode is as follows:

Set i, k to 0.  while k < H′,  if y _(i) is not assigned to RI symbols y _(i) = g _(k)  k = k + 1  end if  i = i+1  end while

The HARQ-ACK information (if present) is written last to the outputmatrix by interleaver 120. Thus, if HARQ-ACK information is to betransmitted in the current subframe, a step 220 tests for whether the RIinformation and the multiplexed data and CQI information has beenalready interleaved. Only after all the other types of input sequenceshave been interleaved does interleaver 120 finally interleave theHARQ-ACK information in a step 225 as follows: the vector sequence q₀^(ACK), q₁ ^(ACK), q₂ ^(ACK), . . . , q_(Q′) _(ACK) ⁻¹ ^(ACK) is writteninto the columns as indicated by Table 2 below and by sets of Q_(m),rows starting from the last row and moving upwards according to thefollowing pseudocode. Note that this operation overwrites some of thechannel interleaver entries obtained from the previous pseudocodediscussion.

Set i,j to 0. Set r to R′_(mux) −1 while i < Q′_(ACK) c_(ACK) =ColumnSet(j) y _(r×C) _(mux) _(+c) _(ACK) = q _(i) ^(ACK) i = i + 1 r =R′_(mux) −1−└i/4┘ j = (j + 3)mod 4 end whileThe Column Set is given in Table 2 and indexed left to right from 0 to3. The output of interleaver 120 is the bit sequence read outcolumn-by-column from the (R_(mux)×C_(mux)) matrix constructed as justdiscussed. The bits after channel interleaving are denoted by h₀, h₁,h₂, . . . , h+Q _(RI) ⁻¹.

TABLE 1 Column set for Insertion of rank information. CP configurationColumn Set Normal {1, 4, 7, 10} Extended {0, 3, 5, 8}

TABLE 2 Column set for Insertion of HARQ-ACK information. CPconfiguration Column Set Normal {2, 3, 8, 9} Extended {1, 2, 6, 7}

Having thus constructed the output matrix, which can be stored in memoryas discussed above, interleaver 120 may then read out the output matrixcolumn-by-column in a step 230 to finish the interleaving process. Theend result of this processing of a transport block is typically denotedas an LTE codeword. The conventional LTE downlink shared channel willnow be discussed.

Downlink Transport Channel Processing in LTE

The transport channel processing for a conventional LTE downlink sharedchannel (DL-SCH) is shown in FIG. 3. For the downlink, the pagingchannel (PCH) and multicast channel (MCH) have the same processing withDL-SCH. The procedures of DL-SCH are quite similar to the UL-SCH. Thistransport channel processing occurs as set forth in LTE Release 9. Dataarrives at a CRC attachment coding unit 300 as a maximum of one MACprotocol data unit (PDU) every transmission time interval (TTI). The MACPDU may be represented by a vector a₀, a₁, a₂, a₃, . . . , a_(A-1) thatis A bits long. Coding unit 100 calculates a corresponding number L ofparity bits p₀, p₁, p₂, p₃, . . . , p_(L-1), where L is determined bythe particular CRC length. In LTE, L can be either sixteen ortwenty-four bits. The bits produced by CRC attachment coding unit 300are represented by a vector b₀, b₁, b₂, b₃, . . . , b_(B-1) of length B,where B equals A plus L. The length B for this vector may be too longfor a subsequent channel coding step that may accommodate only Z bits.This if Z is less than B, the output from coding unit 300 is processedinto shorter blocks with an additional CRC attachment in code blocksegmentation and CRC attachment module 305. The output from module 305may be represented by a vector c_(r) ₀ , e_(r) ₁ , e_(r) ₂ , e_(r) ₃ , .. . , e_(r(E) _(r) _(−1) of) length K_(r). A channel coding module 310receives the output from module 305 and applies the appropriate turbocoding to produce multiple output streams ranging from an i=0 to an i=1stream, where the i^(th) stream may be represented by a vector d_(r) ₁^((i)), d_(r) ₁ ^((i)), d_(r) ₂ ^((i)), . . . , d_(r(D) _(r) ⁻¹⁾ ^((i))of length D_(r)=K_(r)+1. A rate matching module 315 interleaves thestreams from the channel coder and perfoms bit selection and pruning toproduce an output represented by a vector e_(r) ₀ , e_(r) ₁ , e_(r) ₂ ,e_(r) ₃ , . . . , e_(r(E) _(r) ⁻¹⁾ of length E_(r) for code block r. Acode block concentration module 321 concatenates the rate matchingoutputs for the different code blocks to produce an output signalrepresented by a vector f₀, f₁, f₂, f₃, . . . , f_(G-1), of length G.This output signal is the downlink LTE codeword. Thus, the onlydifference from the uplink shared channel processing is that no channelinterleaver is used. Hence, only a set of internal interleavers insiderate matching module 315 help to capture the frequency diversity in aconventional LTE shared downlink channel.

However, all the mechanisms discussed above with regard to FIGS. 1-3 canonly exploit the frequency diversity within one carrier component (CC).In an LTE-Advanced system, each CC fulfills a complete LTE feature set.More CCs will occupy more bandwidth. By interleaving across the wholebandwidth as discussed further herein will capture more frequencydiversity than the conventional carrier aggregation approach in whicheach CC operates separately. A frequency diversity approach that isbackwardly compatible with conventional LTE will now be discussed.

Enhanced Frequency Diversity Exploitation in Carrier Aggregation

To exploit the enhanced frequency diversity opportunity presented bycarrier aggregation (CA), an interleaver functioning across thedifferent CCs is disclosed herein for CA systems. In this fashion,frequency diversity is exploited in carrier aggregation by interleavingbits across component cartiers. In general, backward compatibility withconventional LTE is a significant problem. However, backwardcompatibility is advantageously achieved by the disclosed frequencydiversity technique as discussed further herein. In the downlink sharedchannel, the disclosed CA channel interleaver is added over the CCs,while for the uplink shared channel the proposed interleaver just takesplace of the conventional LTE channel interleaver. The CA channelinterleaver functions as a conventional LTE channel interleaver whenthere is only one CC. The CA channel interleaver exploits enhancedfrequency and time diversity with the advantage of easy implementation.

Uplink Carrier Aggregation Channel Interleaver

To better illustrate the disclosed CA channel interleaver, the followingdiscussion assumes that there are N CCs, where N is some positiveinteger. As shown in FIG. 4, a CA channel interleaver 420 interleaves Nmultiplexed data and CQI information channel-coded portions of the Ntransport blocks, where each multiplexed data and CQI informationchannel-coded portion of the corresponding transport block isrepresented by a vector g₀, g₁, g₂, . . . , g_(H′−1). Each transportblock will have such a portion, ranging from a CC_(—)1 transport blockto a CC_N transport block. Thus, it may be readily seen that modules100, 105, 110, 115, and 110 for each transport block processing operateanalogously as discussed above with regard to FIG. 1. Interleaver 420thus interleaves N combined data and control information signals, eachcombined signal corresponding to the multiplexed data and controlinformation, the RI information, and the HARQ-ACK information for asingle CC transport block. To accommodate these N transport blocks,interleaver 420 includes two stages. A first bit combination stageoccurs in modules 421, 422, and 423. Bit combination module 421 performsa bit combination on the N multiplexed data and CQI information signals.For example, suppose there are just 3 CCs being interleaved such thatthe multiplexed data and CQI information from a first one of the CCs maybe designated as an input sequence [a₁, a₂, . . . , a_(n)], themultiplexed data and CQI information from a second one of the CCs may bedesignated as an input sequence [b₁, b₂, . . . , b_(n)], and themultiplexed data and CQI information from the remaining third CC may bedesignated an input sequence [c₁, c₂, . . . , c_(n)]. Bit combiner 421combines these example input signals to produce a bit-combined outputsignal [a₁, b₁, c₁, a₂, b₂, c₂ . . . , a_(n), b_(n), c_(n)]. In general,the signals being bit combined may be thought of each being arrangedfrom a zeroth word or vector (word 0) to a last word or vector (wordH′−1). Each word has a length of Q_(m) bits as discussed above withregard to multiplexer 125. After interleaving N such input signals, thebit-combined output from combiner 421 will also be arranged from azeroth bit-combined word to a last bit-combined word (word N*H′−1).However, the zeroth to the (N−1) bit-combined output words correspond tothe zeroth words in the N multiplexed data and CQI information signalsbeing bit-combined. Similarly, the N to the (2*N−1) bit-combined outputwords correspond to the first words in the N multiplexed data and CQIinformation signals being bit-combined, and so on such that the(N−1)*(H′−1) to the N*(H′−1) bit-combined output words correspond to thelast words in each of the N multiplexed data and CQI information inputsignals being bit-combined. The resulting bit-combined multiplexed dataand CQI information output signal may thus be designated as [g′₀, g′₁,g′₂, g′₃, . . . g′_(NH′−1].)

Bit combiners 422 and 423 perform analogous bit combinations on the Nchannel-coded RI input signals and the N channel-coded HARQ-ACK inputstreams for the N transport blocks being interleaved. Bit combiner 422thus produces a bit-combined RI output signal designated as [q′₀ ^(RI),q′₁ ^(RI), q′₂ ^(RI), . . . , q_(NQ′) _(RI) ⁻¹ ^(RI)] whereas bitcombiner 423 produces a bit-combined HARQ-ACK output signal designatedas [q′₀ ^(ACK), q′₁ ^(ACK), q′₂ ^(ACK), . . . , q′_(NQ′) _(ACK) ⁻¹^(ACK)].

The second stage for CA channel interleaver 420 is a channel interleaver425 that interleaves the three bit-combined output signals produced inthe bit-combining first stage. The number of modulation symbols in eachsubframe is given by H″=N (H′+Q′_(RI)). Channel interleaver 425 isconfigured to derive its output bit sequence as follows: Interleaver 425writes to an output matrix that may be stored in a memory or buffer asanalogously described above with regard to conventional LTE processing.The number of columns for this output matrix is given byC_(mux)=N_(symb) ^(PUSCH). The columns of the matrix are numbered 0, 1,2, . . . , C_(mux)−1 from left to right as also previously discussed.However, the number of rows is given by R_(mux)=(H″·Q_(m))/C_(mux),which is N times of the number of rows in LTE UL. Each continuous blockof R_(mux)/N rows in the output matrix may be considered to form asub-matrix that corresponds to one CC. There are thus N sub-matrices inthe output matrix corresponding to the N CCs.

FIG. 5 illustrates the interleaving process performed by interleaver425. In an initial step 500, interleaver 425 determines the number N ofcomponent carriers being aggregated so that the appropriate bitcombination may be performed in a step 505. Interleaver 425 may thenidentify what type of bit-combined signal is currently being processedin a step 510. There are then 3 paths to take depending upon whetherstep 510 identifies data/CQI information, RI information, or HARQ-ACKinformation. If RI information is included in this subframe, then the RIinformation is written first to the output matrix. Thus, a step 515delays the processing of data/CQI information until the RI informationhas been interleaved into the output matrix.

RI information is processed in a step 520 by being segmented into Nequal subsequences. For example, if the input to step 510 is consideredto form an input signal [a₁, a₂, . . . , a_(n)], then the output fromstep 520 forms the N subsequences [a₁, a₂, . . . , a_(n/N)], . . . ,[a_(n-n/N+1), a_(n-n/N+2), . . . , a_(n)]. Each subsequence correspondsto a CC transport block. Each subsequence is interleaved into thecorresponding carrier component sub-matrix in a step 525 following theway discussed above with regard to step 210 of FIG. 2. However, whereasstep 210 of FIG. 2 is interleaving the RI information into the entireoutput matrix, step 525 is merely interleaving into the correspondingsub-matrix.

With RI information interleaving completed, the data/CQI information mayinterleaved in a step 530 by writing the input vector sequence, for k=0,1, . . . , NH′−1 into the (R_(mux)×C_(mux)) output matrix by sets ofQ_(m) rows starting with the vector y₀ in column 0 and rows 0 to(Q_(m)−1) and skipping the matrix entries that are already occupied byRI information as:

$\begin{bmatrix}{\underset{\_}{y}}_{0} & {\underset{\_}{y}}_{1} & {\underset{\_}{y}}_{2} & \ldots & {\underset{\_}{y}}_{C_{mux} - 1} \\{\underset{\_}{y}}_{C_{mux}} & {\underset{\_}{y}}_{C_{mux} + 1} & {\underset{\_}{y}}_{C_{mux} + 2} & \ldots & {\underset{\_}{y}}_{{2C_{mux}} - 1} \\\vdots & \vdots & \vdots & \ddots & \vdots \\{\underset{\_}{y}}_{{({R_{mux}^{\prime} - 1})} \times C_{mux}} & {\underset{\_}{y}}_{{{({R_{mux}^{\prime} - 1})} \times C_{mux}} + 1} & {\underset{\_}{y}}_{{{({R_{mux}^{\prime} - 1})} \times C_{mux}} + 2} & \ldots & {\underset{\_}{y}}_{({{R_{mux}^{\prime} \times C_{mux}} - 1})}\end{bmatrix}\quad$

where R′_(mux)=R_(mux)/Q_(mux).

The HARQ-ACK information is written into the output matrix only afterthe RI information and the data/CQI information has been processed.Thus, a step 535 delays the interleaving of the HARQ-ACK informationaccordingly. Once step 535 determines that the RI information and thedata/CQI information has been processed, the HARQ-ACK information issegmented in a step 540 in same way as discussed with regard to step525. Each resulting subsequence corresponds to a carrier component andis interleaved in a step 545 into the corresponding CC sub-matrix asdiscussed with regard to step 225 of FIG. 2. However, whereas step 225discusses interleaving into an entire output matrix, the output matrixfor step 545 is instead the corresponding sub-matrix.

With the output matrix thus completed, the component carrier data may beread from the corresponding sub-matrix column-by-column in a final step550. The result would be N output code words for the N componentcarriers. It can readily be seen that if N=1, the CA channel interleaver420 performs exactly the same as the conventional 120 channelinterleaver discussed with regard to FIG. 1. Therefore, backwardcompatibility with LTE UL is advantageously achieved. Carrieraggregation for the shared downlink channel will now be discussed.

Downlink Carrier Aggregation Channel Interleaver

As shown in FIG. 6, a downlink carrier aggregation channel interleaver620 includes a bit combining stage and an interleaving stage asanalogously discussed above with regard to the uplink shared channel. Abit combiner 630 bit combines the channel-coded outputs from each of theN component carrier channels. The channel coding within each componentcarrier channel occurs as discussed with regard to FIG. 3. Thus eachcomponent carrier channel CC_(—)1 through CC_N includesalready-described modules 300, 305, 310, 315, and 321. Bit combinationstage 630 thus bit combines N input channel-coded transport blocks inthe same fashion as discussed with regard to combiners 421 through 423of FIG. 4.

The resulting bit-combined output from combiner 630 is received by acarrier aggregation channel interleaver 640. FIG. 7 illustrates thechannel interleaving process performed by interleaver 640. In an initialstep 700, the number N of component carriers being aggregated isdetermined. Since there is no channel interleaving in a conventional LTEshared downlink channel, interleaver 640 and bit combiner 630 checkwhether N equals one in a step 705. If N equals one (no carrieraggregation), the remaining steps in FIG. 7 are skipped. If N is greaterthan one, bit combiner 630 performs a bit combination step 710 asdiscussed analogously with regard to step 505 of FIG. 5. The data canthen be interleaved into an output matrix within an associated memory byinterleaver 640 in a step 715 as follows: Assign C_(mux)=N_(symb)^(PUSCH) to be the number of columns of the matrix, where C_(mux) isdefined as discussed above. The columns of the output matrix arenumbered 0, 1, 2, . . . , C_(mux)−1 from left to right. The number ofmodulation symbols in each subframe is given by H′=N*G, where G is asdefined as discussed above with regard to module 321. The number of rowsof the matrix is given by R_(mux), where R_(mux)=H′Q_(m)/C_(mux), and wealso have R′_(mux)=R_(mux)/Q_(m). Each continuous set of R_(mux)/N rowsof the output matrix maybe considered to form a sub-matrix. There arethus N sub-matrices corresponding to the N component carriers.Interleaver 640 writes the input vector sequence, for k=0, 1, . . . ,NH′−1 into the (R_(mux)×C_(mux)) output matrix by sets of Q_(m), rowsstarting with the vector y₀ in column 0 and rows 0 to (Q_(m)−1) andskipping the matrix entries that are already occupied by RI informationas:

$\begin{bmatrix}{\underset{\_}{y}}_{0} & {\underset{\_}{y}}_{1} & {\underset{\_}{y}}_{2} & \ldots & {\underset{\_}{y}}_{C_{mux} - 1} \\{\underset{\_}{y}}_{C_{mux}} & {\underset{\_}{y}}_{C_{mux} + 1} & {\underset{\_}{y}}_{C_{mux} + 2} & \ldots & {\underset{\_}{y}}_{{2C_{mux}} - 1} \\\vdots & \vdots & \vdots & \ddots & \vdots \\{\underset{\_}{y}}_{{({R_{mux}^{\prime} - 1})} \times C_{mux}} & {\underset{\_}{y}}_{{{({R_{mux}^{\prime} - 1})} \times C_{mux}} + 1} & {\underset{\_}{y}}_{{{({R_{mux}^{\prime} - 1})} \times C_{mux}} + 2} & \ldots & {\underset{\_}{y}}_{({{R_{mux}^{\prime} \times C_{mux}} - 1})}\end{bmatrix}\quad$

Each carrier component is read from its sub-matrix column-by-column in astep 720 to complete the downlink processing. Each sub-matrix thuscorresponds to a component carrier code word. One can observe from FIG.7 that if N=1, the proposed channel interleaver will be skipped, thusmaintaining compatibility with LTE DL.

The above carrier aggregation process may be entirely implemented atbaseband and is thus readily implemented in a baseband processor. FIG. 8illustrates a generic radio architecture that may represent either abase station (for the downlink) or a user equipment (for the uplink).Radio 800 includes a radio frequency integrated circuit (RFIC) 805 thatreceives a baseband signal 810 from a baseband processor 815. Basebandsignal 810 could be the baseband uplink or downlink signal dependingupon whether radio 800 is implementing a user equipment or a basestation, respectively. A DAC 820 converts signal 810 into analog form sothat it may modulate an RF carrier (or carriers) produced by anoscillator 820 within a modulator 840. A power amplifier 845 amplifiesthe resulting modulated RF signal so that it may be transmitted by anantenna (or antennas) 850. A receive RF path is also shown within RFIC805 although this path is not important for the uplink and downlinkprocessing disclosed herein and will thus not be discussed in furtherdetail.

Baseband processor 815 may be programmable such that it implements thedownlink or uplink modules discussed above using software implemented ona microprocessor or through programmed logic resources within an FPGA.Alternatively, baseband processor 815 may be a dedicated ASIC.Regardless of how the baseband processing is implemented, it willadvantageously interleave the downlink or uplink shared channel acrossthe component carriers to exploit frequency diversity as discussedherein.

Embodiments described above illustrate but do not limit the disclosure.It should also be understood that numerous modifications and variationsare possible in accordance with the principles of the presentdisclosure. For example, although the frequency diversity exploitationdiscussed above was regard to an LTE enhancement, it will be appreciatedthat the same technique can be readily applied to other high speedwireless protocols such as WiMax. Accordingly, the scope of thedisclosure is defined only by the following claims.

1. A method, comprising: providing a plurality of transport blocks, eachtransport block corresponding to a component carrier (CC) such that aplurality of component carriers corresponds to the plurality oftransport blocks; in a baseband processor, channel coding a data portionof each transport block into a corresponding channel-coded input datasignal; in the baseband processor, bit-combining the channel-coded inputdata signals into a bit-combined data signal; and in the basebandprocessor, interleaving the bit-combined data signal to produce aninterleaved plurality of code words corresponding to the plurality ofcomponent carriers.
 2. The method of claim 1, wherein the transportblocks are uplink shared channel transport blocks.
 3. The method ofclaim 2, further comprising: in the baseband processor, channel coding acontrol quality information (CQI) portion of each transport block into acorresponding channel-coded CQI signal; and in the baseband processor,multiplexing each channel-coded input data signal with a correspondingone of the channel-coded CQI signals to produce a plurality ofmultiplexed data signals, wherein bit-combining the channel-coded datasignals comprises bit-combining the multiplexed data signals.
 4. Themethod of claim 3, further comprising: channel coding a rank indication(RI) portion of each transport block into a corresponding channel-codedRI signal; channel coding a HARQ-ACK portion of each transport blockinto a corresponding channel-coded HARQ-ACK signal; bit-combining thechannel-coded RI signals into a bit-combined RI signal; bit-combiningthe channel-coded HARQ-ACK signals into a bit-combined HARQ-ACK signal,wherein interleaving the bit-combined data signal comprises interleavingthe bit-combined data signal with the bit-combined RI and HARQ-ACKsignals.
 5. The method of claim 4, wherein interleaving the bit-combinedRI signal comprises separating the bit-combined RI signal into aplurality of RI subsequences corresponding to the plurality of componentcarriers, and interleaving each RI subsequence.
 6. The method of claim4, wherein interleaving the bit-combined HARQ-ACK signal comprisesseparating the bit-combined HARQ-ACK signal into a plurality of HARQ-ACKsubsequences corresponding to the plurality of component carriers, andinterleaving each HARQ-ACK subsequence.
 7. The method of claim 1,wherein the transport blocks are downlink shared channel transportblocks.
 8. A downlink method, comprising determining whether a pluralityof component carriers are being interleaved; if a plurality of componentcarriers are being interleaved, bit-combining a plurality ofchannel-coded data signals to form a bit-combined data signal; writingthe bit-combined data signal into an interleaver matrix stored within amemory, wherein the interleaver matrix is arranged into a plurality ofsub-matrices corresponding to the plurality of component carriers;reading from each sub-matrix to retrieve a corresponding output codeword; and modulating each component carrier according to thecorresponding output code word.
 9. The downlink method of claim 8,wherein Q_(m) represents a modulation order, and wherein thebit-combined data signal is written into the interleaver matrix a set ofQ_(m) rows at a time.
 10. A wireless device, comprising: a memory; abaseband processor configured to channel code a plurality transportblocks data portions into a corresponding plurality of channel-codeddata signals, bit-combine the channel-coded data signals into abit-combined data signal, write the bit-combined data signal into aninterleaver matrix stored within the memory, and to read from theinterleaver matrix to produce an interleaved plurality of code words;and a radio-frequency integrated circuit (RFIC) configured to modulatean RF carrier signal according to the interleaved plurality of codewords.
 11. The wireless device of claim 10, wherein the transport blocksare uplink shared channel transport blocks.
 12. The wireless device ofclaim 11, wherein the baseband processor is further configured tochannel code a plurality of channel quality information (CQI) controlsignal transport block portions into a corresponding channel-coded CQIdata signal, and to multiplex each channel-coded data signal with acorresponding one of the channel-coded CQI data signals to produce aplurality of multiplexed data signals, and wherein the basebandprocessor is configured to bit-combine the channel-coded data signals bybit-combining the multiplexed data signals.
 13. The wireless device ofclaim 12, wherein the baseband processor is further configured tochannel code a plurality of rank indication (RI) and hybrid repeatrequest acknowledgment (HARQ-ACK) transport block portions correspondingto provide channel-coded RI signals and channel-coded HARQ-ACK signals,and to bit-combine the channel-coded RI signals into a bit-combined RIsignal, and to bit-combine the channel-coded HARQ-ACK signals into abit-combined HARQ-ACK signal, and wherein the baseband processor isconfigured to interleave the bit-combined data signals with thebit-combined RI and HARQ-ACK signals.
 14. The wireless device of claim13, wherein the baseband processor is configured to interleave thebit-combined RI signal by separating the bit-combined RI signal into aplurality of RI subsequences corresponding to the plurality of componentcarriers, and to interleave each RI subsequence.
 15. The wireless deviceof claim 14, wherein the baseband processor is configured to interleavethe bit-combined HARQ-ACK signal by separating the bit-combined HARQ-ACKsignal into a plurality of HARQ-ACK subsequences corresponding to theplurality of component carriers, and to interleave each HARQ-ACKsubsequence.
 16. The wireless device of claim 15, wherein the wirelessdevice comprises an LTE-Advanced user equipment.
 17. The wireless deviceof claim 10, wherein the transport blocks are downlink shared channeltransport blocks.
 18. The wireless device of claim 17, wherein thewireless device is an LTE-Advanced base station.
 19. The wireless deviceof claim 10, wherein each channel-coded data signal is arranged from afirst channel-coded digital word to a last channel-coded digital word,and wherein the baseband processor is configured to bit-combine thechannel-coded data signals such that the bit-combined data signal isarranged from a first bit-combined digital word to a last bit-combineddigital word corresponding to the digital words in each of thechannel-coded data signals, wherein each bit-combined digital word is acombination of the corresponding channel-coded digital words.
 20. Thewireless device of claim 10, wherein the baseband processor is furtherconfigured to read from the interleaver matrix row-by-row to produce theinterleaved plurality of code words.